Metal-bearing paste and aluminum connection containing the same



Jan. 13, 1959 F. H. WELLS 2,869,103 METAL-BEARING PASTE AND ALUMINUM CONNECTION CONTAINING THE SAME Filed June 2, 1955 AIM/(2 PART/C153 IN AN NCH/0V3 HEDIUM INVENTOR.

Franklin Wei/s BY United States Patent Franklin H. Wells, Harrisburg, Pa., assignor to AMP Incorporated, a corporation of New Jersey Application June 2, 1953, Serial No. 359,201

Claims. (Cl. 339-115) This invention relates to the production of electrical connections to aluminum conductors and more particularly to a metal-bearing paste adapted to be used in crimping terminals to aluminum conductors to improve the electrical properties of the crimped connection. This application is a continuation-in-part of application Serial Number 358,190 filed May 28,1953, by Franklin H. Wells, and now abandoned.

The principal objective sought in the making of connections between electrical conductors is the attainment of a joint having minimum electrical resistance. Moreover, it is desirable that the joint not only have a low initial resistance but also that this low resistance be maintained over a considerable period of time. In making connections wherein one or both of the elements to be joined are made of aluminum a special problem is presented because of the oxide coating on the aluminum which must be removed or pierced to make a low resistance connection. Also, in order to achieve a connection wherein the .resistance remains at a relatively low value, it is necessary that the joint be protected against the corrosive elfects of atmospheric oxygen and water vapor.

One previously proposed method of improving the electrical conductivity and stability of electrical connections of the type referred to above involves the application to the parts to be joined of a paste comprising an unctuous or oleaginous medium having finely divided solid particles dispersed therein. It is an object of the present invention to provide an improved paste of this character. It is another object of the invention to provide a termination for an aluminum conductor that has a relatively low and stable electrical resistance. It is a further object of the invention to improve the electrical properties of joints formed by crimping terminals to the. ends of aluminum conductors.

In the drawing:

.Figure 1 is a side view of a connector and a conductor, the connector containing a paste in accordance with the invention; and

Figure 2 is a view showing the connector crimped onto the conductor.

It has been found that connections to aluminum conductors which have exceptionally low resistance and which" remain stable over considerable periods of time can be made by using as a joint compound a paste comprising finely divided nickel powder dispersed in an unctuous or oleaginous medium. The nickel powder used preferably has a particle size such that substantially all of it passes through a 300 (46 microns) mesh screen and good results have been obtained when using a nickel powder having a nominal particle size of 5 microns. Equivalent results have been obtained when using the so-called molding" and non-molding powders. A variety of unctuous media can be used in forming the nickel powder paste. Good results have been obtained by using as the unctuous medium a non-melting grease composed essentially of modified bentonite. The bentonite grease is a known product prepared by base-ex- 2,869,103 Patented Jan. 13, 1959 changing bentonite with an organic amine and combining the resulting product with a conventional lubricating oil. Another suitable medium in which the nickel powder can be dispersed is petrolatum.

The proportions of nickel to oil or grease in the paste can be varied over relatively wide limits, say from 25% to by weight of the nickel powder. If less than 25% by weight of nickel is used in the paste the effectiveness of the paste in providing a stable electrical connection diminishes significantly. The upper limit is largely determined by the physical characteristics of the paste, that is to say, if an excessive proportion of nickel is used the resulting composition lacks the desired plasticity. Since the plasticity of the paste is to some extent a function of the nature of the greasy medium in which the nickel is dispersed, this upper limit depends in some measure upon what type of greasy medium is used. However, it is generally undesirable to use more than 90% by Weight of the nickel powder and in most cases a mixture of approximately equal weights of nickel powder and unctuous medium give preferred results.

The paste of the present invention can be used in a variety of ways to improve the electrical properties of joints between electrical elements, either or both of which are composed of aluminum. To illustrate the mode of use of the present paste assume that it is desired to terminate an aluminum conductor with a terminal of the type shown in Freedom Patent 2,535,013. Such terminals comprise a perforated tongue portion adapted to be connected to a binding post or the like and a barrel portion in which the end of a conductor is positioned and crimped by pressure applied to the exterior of the barrel.

In making a connection of this type in accordance with the present invention, the barrel portion 2 of the terminal is filled with the nickel paste and the bareend 4 of the aluminum conductor forced into the paste within the barrel of the terminal, after which the terminal is crimped on the conductor, as shown at 6, in the usual manner. Crimped connections made in this way have been tested in comparison with similar crimped joints in which no nickel paste was used as well as in comparison with crimped joints made with other types of joint compound and it has been found that the crimped connections made with the present paste when heated in air for long periods of time at about C. are sub stantially superior in their stability to either the crimped connections in which no paste was used or to the connections in which paste containing other dispersed particles were used.

The superiority of the persent nickel powder paste is shown by the data set forth in the table below. The data of the table were obtained in the following manner:

A series of pastes were made up comprising 50% by weight petrolatum and 50% by weight of the various powdered metals and metal compounds listed in the left hand column of the table. A set of ten connections was made using each of these pastes in the general manner described above. The terminals used were tin-plated cop per and were of the type shown in Freedom Patent 2,535,013. In each case the barrel portion of the terminal was filled with the paste, a No. 4 aluminum conductor inserted in the barrel, and the terminal crimped on the end ofthe conductor.

After crimping the connections were placed in an oven maintained at 100 C. for a period of several months. Once or twice in each twenty-four hour period connections were removed from the oven for about one hour and permitted to cool to room temperature. At intervals the terminals were tested to determine their electrical resistance by passing a current of 101 amperes therethrough and measuring the voltage drop across the connection in millivolts. For each set of ten terminals the maximum resistance, minimum resistance and average resistance were noted. The data set forth in the table comprise the maximum, minimum and average values of resistance 5 for each set of ten test terminals at about the time they were crimped and also at the end of 119 days of heat cycling. For purposes of comparison a set of connections was made using petrolatum alone and the values for this set of connections are given at the top of the table.

Tabla Initial Voltage Drop after 119 days Drop (milli'vo'lts) (millivolts) Min. Max. Av. Min. Max. Av.

Petrolatum 3' 5 4 23 145 35 Nickei.- 2 4 3 o 5 22.5 18.5 Zinc 2 3 2.5 7 46 20 Silicon Carbide. 2 3.5 3 27 245 125.5 Aluminum--. 2 -4 3 39 320 105 Manganese... 2. 3 2.5 365 122 Tin 2 4 3 32 400 17s Lead 2 3 2.5 17 4s 3s Magnesium 2 4 3 38 285 128 Titanium Dioxide 1. 5 3 2 40 27. 5 Iron oxide (F6203) 2 3.5 2.5 22 5 210 25 Iron oxide (FeaO4) 1. 5 3 2 310 59. 5 Antimony 2 4 3 100 400 208 Chromium 1 3 2 150 340 245.5 Ghromlc Oxide 3 13 7.5 40 100 Ohromous Oxide." 1. 5 3 2 38 310 220. 5 Manganese Dioxide 2.5 3. 2.6 215 500+ 3 1.5 3 2 310 216 30 Cobalt oxide (000 1 2.5 2 225 400 316 Indium 2 3 2.5 325 405 355 Tin Oxide (SI102) 1 2.5 2 55 385 232.5 Vanadium Oxide (V204) 2 3.5 3 500+ 286.5 Vanadium 1 2.5 2 39 99 l erro-Vanadiurn... 1 2 1.5 37 320 143 The data of the table clearly bring out the superiority of the present nickel paste and show that it is substantially superior to'any of the other 23 pastes that were tested. It may be noted "that the maximum value-of the voltage drop for the set-of connections made with nickel paste is less than the average value of voltage drop for the set of connections made with any of the other pastes tested. The strikingly superior effectiveness of the nickel paste is a surprising result and manifestly could not have been pre- 4 dicted on the basis of the known chemical and physical properties of the nickel powder as compared with the properties of the other metals and compounds tested.

From the foregoing escription it should be apparent that the present invention provides a substantially im proved paste for use in making connections to aluminum conductors and provides improved connections made therefrom having exceptional stability over relatively long periods of time. It is, of course, to be understood that the foregoing description is illustrative and that various 55 oleagiuous media can be used for dispersing the nickel powder to form a paste and that the paste can be used in a variety of terminals and connectors to provide crimped connections to aluminum conductors, all without departnickel powder based on the total Weight of petrolatum' and nickel.

2. A metal-bearing paste adapted to be used in the crimping of connectors to aluminum conductors to improve the electrical properties of the resulting crimped connection, said paste consisting essentially of petrolatum containing from 25% to 90% by weight of finely divided nickel powder based on the total weight of petrolatum and nickel, substantially all of said nickel power being of a particle size which will pass a 300 mesh screen.

3. A crimped electrical connection comprising an electrical connector having a cylindrical portion made of an electrically-conductive metal, said cylindrical portion c'ontaining 21 body of a paste comprising a finely divided nickel powder dispersed in petrolatum, said nickel powder comprising from 25% to 90% by weight of said paste, and an aluminum conductor positioned in said body of paste within said cylindrical portion of said connector.

4. A crimped electrical connection comprising an elec trical connector having a cylindrical portion made of an electrically conductive metal, said cylindrical portion containing a body of a paste comprising a finely divided nickel powder dispersed in an unctuous medium, said nickel powder comprising 25% to 90% by weight of said paste, and an aluminum conductor positioned in said body of paste within said cylindrical portion of said connector, said cylindrical portion being crimped to said aluminum conductor through said body of paste.

5. A crimped electrical connection comprising an electrical connector having a cylindrical portion made of an electrically conductive metal, said cylindrical portion containinga body of a paste consisting essentially of finely divided nickel powder dispersed in petrolatum, said nickel powder being present to the extent of 25% to 90% by weight of said paste and having a particle size such that substantially all of the nickel powder passes a 300-mesh screen and an aluminum conductor positioned in said body of paste within said cylindrical portion of said connector, said cylindrical portion being crimped to said aluminum conductor through said body of paste.

References Cited in the file of this patent UNITED STATES PATENTS 711,123 Rhoades Oct. 14, 1902 1,863,429 Willmore June 14, 1932 1,994,849 Bauza Mar. 19, 1935 2,280,135 Ward Apr. 21, 1942 2,423,290 Bonwitt July 1, 1947 2,441,945 Frolich et al. May 25, 1948 2,570,856 Pratt Oct. 9, 1951 2,702,756 Kurlandsky Feb. 22, 1955 

4. A CRIMPED ELECTRICAL CONNECTION COMPRISING AN ELECTRICAL CONNECTOR HAVING A CYLINDRICAL PORTION MADE OF AN ELECTRICALLY CONDUCTIVE METAL, SAID CYLINDRICAL PORTION CONTAINING A BODY OF A PASTE COMPRISING A FINELY DIVIDED NICKEL POWDER DISPERSED IN AN UNCTUOUS MEDIUM, SAID NICKEL POWDER COMPRISING 25% TO 90% BY WEIGHT OF SAID PASTE, AND AN ALUMINUM CONDUCTOR POSITIONED IN SAID BODY OF PASTE WITHIN SAID CYLINDRICAL PORTION OF SAID CONNECTOR, SAID CYLINDRICAL PORTION BEING CRIMPED TO SAID ALUMINUM CONDUCTOR THROUGH SAID BODY OF PASTE. 